const ExtractTextPlugin = require('extract-text-webpack-plugin');

exports.cssLoaders = (_options) => {
  const options = _options || {};

  const cssLoader = {
    loader: 'css-loader',
    options: {
      sourceMap: options.sourceMap
    }
  };

  // generate loader string to be used with extract text plugin
  function generateLoaders(loader, loaderOptions) {
    const loaders = [cssLoader];
    if (loader) {
      // add postcss
      loaders.push({
        loader: 'postcss-loader',
        options: {
          sourceMap: options.sourceMap
        }
      });
      loaders.push({
        loader: `${loader}-loader`,
        options: Object.assign({}, loaderOptions, {
          sourceMap: options.sourceMap
        })
      });
    }

    // Extract CSS when that option is specified
    // (which is the case during production build)
    if (options.extract) {
      return ExtractTextPlugin.extract({
        use: loaders,
        fallback: 'vue-style-loader'
      });
    }
    return ['vue-style-loader'].concat(loaders);
  }

  // https://vue-loader.vuejs.org/en/configurations/extract-css.html
  return {
    css: generateLoaders(),
    less: generateLoaders('less'),
    // sass: generateLoaders('sass', { indentedSyntax: true }),
    // scss: generateLoaders('sass'),
    // stylus: generateLoaders('stylus'),
    // styl: generateLoaders('stylus')
  };
};

// Generate loaders for standalone style files (outside of .vue)
exports.styleLoaders = (options) => {
  const output = [];
  const loaders = exports.cssLoaders(options);
  for (const extension in loaders) {
    const loader = loaders[extension];
    output.push({
      test: new RegExp(`\\.${extension}$`),
      use: loader
    });
  }
  return output;
};
